CHAPTER 3: Key Principles of Engineering and Science for environmental problem

1. CHAPTER 3: Key Principles of
Engineering and Science for
environmental problem
Prepared by: Shaheen Sardar
COURSE TITLE: Environmental issues of textile
industry

2. Key Principles of Engineering and
Science for environmental problem
Introduction:
• In this Chapter we will review following key
principles.
(1) Mass and energy transfer
(2) Environmental chemistry
(3) Mathematics of growth
(4) Risk assessment

3. MASS AND ENERGY TRANSFER
• Law of conservation of mass says “When
chemical reactions take place, matter is
neither created nor destroyed. (Though in
nuclear reactions mass can be converted to
energy). This law shows that pollutants have
to go somewhere. We should be careful about
approaches that transport them from one
medium to another.

4. Law of conservation of mass

5. MASS AND ENERGY TRANSFER
• First law of thermodynamics says “Energy can
neither be created nor destroyed, energy may
change forms”

6. First law of thermodynamics

7. MASS AND ENERGY TRANSFER
• Second law of thermodynamics says “There
will always be some waste heat. How that
waste heat affects the environment is an
important consideration in the study of
environmental engineering and science. It is
impossible to devise a machine that can
convert heat to work with 100% efficiency.
There will always be losses.

8. Second law of thermodynamics

9. ENVIRONMENTAL CHEMISTRY
• Almost every pollution problem that we face
has a chemical basis.
• In Stoichiometry, we use law of conservation
of mass to balance chemical equations.
N2 + 3H2 → 2NH3
• We use law of conservation of energy to learn
something about heat absorbed or released
during chemical reactions. Since energy must
be conserved, we should be able to track it
from beginning to end.

10. Law of conservation of energy

11. ENVIRONMENTAL CHEMISTRY
• When the rates of reaction are same in both
directions, the reaction is said to have reached
equilibrium.
• Organic chemistry is the chemistry of
compounds of carbons.
• Nuclear chemistry is the chemistry of
radioactive substances. It is the Study of the
atomic nucleus, including fission and fusion
reactions and their products.

12. Nuclear chemistry

13. MATHEMATICS OF GROWTH
• It is used to shed light on the number of
environmental problems including population
growth, resource consumption, pollution
accumulation, and radioactive decay.

14. MATHEMATICS OF GROWTH

15. MATHEMATICS OF GROWTH

16. RISK ASSESSMENT
• Risk = Hazard x Exposure
• Risk assessment is the gathering of data that
are used to relate response to dose. The data
can be combined with estimates of likely
human exposure to produce overall
assessments of risk.

17. RISK ASSESSMENT

18. RISK ASSESSMENT

19. Risk management
• Risk management is the decision making
about how to allocate national resources to
protect public health and the environment.

20. Risk management

21. RISK ASSESSMENT
• Our concern is with the probability that
exposure of some number of people to some
combination of chemicals will cause some
amount of response, such as cancer,
reproductive failure, neurological damage,
development problems, or birth defects.
• Risk assessment is usually considered to be a
four step process followed by risk
management.

22. RISK ASSESSMENT
Hazard identification
Dose-Response Assessment Exposure assessment
Risk characterization
Risk Management

23. RISK ASSESSMENT
(1) Hazard identification:
• It is the process to determine whether or not
the chemicals are linked with adverse health
effects.

24. Hazard identification

25. RISK ASSESSMENT
(2) Dose-Response Assessment:
• Process to obtain a mathematical relationship
between the amount of a toxicant that a
human is exposed to and the risk that there
will be an unhealthy response to that dose.

26. Dose-Response Assessment

27. RISK ASSESSMENT
(3) Human Exposure assessment:
• It is two-step process as follows;
• (a) Pathways that allow toxic agents to be
transported from source to the point of
contact with people must be evaluated.
• (b) An estimate must be made of the amount
of contact that is likely to occur between
people and those contaminants.

28. Human Exposure assessment

29. RISK ASSESSMENT
(4) Risk characterization:
• It is the integration of the forgoing 3-steps,
which results in an estimate of the magnitude
of the public-health problem.
• This phase determines the probability of an
adverse effect to a human population by a
toxic substance and outlines permissible
exposure levels from which standards of
exposure are set.